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Climate and Construction: New OBC ventilation requirements criticized as counterproductive

John Bleasby
Climate and Construction: New OBC ventilation requirements criticized as counterproductive

Concerns are mounting regarding the new Ontario Building Code (OBC). Several building envelope scientists and energy-efficiency experts say the provincial code, based on the 2020NBC, represents a “step backward” and is not outcome-based. The proposed OBC could also be counterproductive to Canada’s international obligations.

Passive House Canada CEO Chris Ballard has submitted recommendations to address OBC shortcomings that make building homes to Passive House standards more difficult. Building policy consultant Rob Bernhardt recently told the Daily Commercial News that 2020NBC’s adoption of the Reference Building Approach (RBA) to predict the energy use in proposed buildings can actually penalize energy-efficient building designs.

The latest criticisms being expressed surround how Ontario’s proposed code could negatively impact indoor comfort, air quality and energy use in both Part 9 and Part 3 buildings, particularly multi-family residential projects built to Passive House standards. These are regarded globally as the gold standard in energy efficiency and interior comfort.

It has to do with ventilation rates. Ontario does not have its own air ventilation standards and has traditionally relied largely on those set out by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). At issue is the high continuous ventilation rates required under ASHRAE 62.1 are far higher than those required by Passive House.

Deborah Byrne, director of Passive House design at Kearns Mancini Architects in Toronto, believes COVID also triggered a response from ASHRAE to add even more ventilation to reduce potential transmissions. However, she says this mandate does not make sense in a Passive House building.

“ASHRAE’s response to COVID was a bulletin that basically said to further increase those rates and run the system 24/7,” she told the Daily Commercial News. However, she points out ASHRAE works in isolation of other factors, notably the building envelope, the operation of the building and the people in it.

“None of that is taken into account. ASHRAE is just a number.”

“Those numbers are not relevant to buildings with high performing envelopes, such as Passive Houses,” says Esther van Eeden, sustainability lead at Kearns Mancini. “Targeting a prescriptive number while ignoring other contributing factors seems counterintuitive when we have access to tools that can prove building performance.”

Furthermore, ventilation under ASHRAE 62.1 is one way and unbalanced, requiring the over-extraction and then over-supply of air. This not only uses more operational energy, but also sucks air out that has been heated or cooled by mechanical systems. Therefore more energy is expended to heat or cool the replacement air that must be brought in from outside.

As of yet, ASHRAE does not have specific standards recognizing Passive House requirements. However, Ontario’s building code has allowed ASHRAE 62.2 to this point. Although requiring fewer air changes than 62.1 — and still more than required by Passive House — it’s been a manageable trade-off. Nevertheless, permission to use 62.2 is needed from the permit issuing authority. It also requires measurement and verification, concepts the construction industry instinctively opposes at every turn.

The building envelopes of Passive Houses are part of the overall heating system, something code developers have failed to recognize, says Byrne. Therefore, Passive House designs require fewer air changes while providing a higher quality standard of air than ASHRAE 62.1. They achieve this using low-energy, balanced ventilation arrangements that deliver constant supplies of fresh filtered air 24/7, with heat recovery to bedrooms and living rooms at a volume equal to the exhaust air removed from kitchens and bathrooms.

“Each and every Passive House multifamily building design in Ontario will struggle under the OBC’s ASHRAE 62.1 ventilation code requirements,” says Byrne.

It will also affect Toronto Green Standards objectives that promote more stringent Thermal Energy Demand Intensities in the city’s projects, including public housing.

Byrne joins several experts critical of the random nature of Canada’s building code development.

“It comes down to the usual thing of the left hand not knowing what the right hand is doing. None of the codes right now are taking a science-based approach.”

John Bleasby is a Coldwater, Ont.-based freelance writer. Send comments and Climate and Construction column ideas to

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